Satellite dwarf galaxies: stripped but not quenched

Abstract

In the Local Group, quenched gas-poor dwarfs galaxies are most often found close to the Milky Way and Andromeda, while star forming gas-rich ones are located at greater distances. This so-called morphology-density relation is often interpreted as the consequence of the ram pressure stripping of the satellites during their interaction with the Milky Way hot halo gas. While this process has been often investigated, self-consistent high resolution simulations were still missing. In this study, we have analysed the impact of both the ram pressure and tidal forces induced by a host galaxy on dwarf models as realistic as possible emerging from cosmological simulations. These models were re-simulated using both a wind tunnel and a moving box technique. The secular mass growth of the central host galaxy, as well as the gas density and temperature profiles of its hot halo have been taken into account. We show that while ram pressure is very efficient at stripping the hot and diffuse gas of the dwarf galaxies, it can remove their cold gas (T < 10 3 [K]) only in very specific conditions. Depending on the infall time of the satellites relatively to the build-up stage of the massive host, star formation can thus be prolonged instead of being quenched. This is the direct consequence of the clumpy nature of the cold gas and the thermal pressure the hot gas exerts onto it. We discuss the possibility that the variety in satellite populations among Milky Way-like galaxies reflects their accretion histories.

Molecular gas and star formation activity in luminous infrared galaxies in clusters at intermediate redshifts

“…We discussed possible scenarios to explain the presence of significant large reservoirs of molecular gas in the LIRGs from the outskirts down to the cluster cores as well as the rising of the star formation with decreasing cluster-centric distance. The presence of enhanced star formation activity observed in a large fraction of the LIRGs within the virial radius suggests that environmental processing mechanisms such as ram-pressure stripping, galaxy harassment, and starvation may have not been sufficiently effective in suppressing the star formation and then quenching the LIRGs, consistently with recent results found in simulations (Hausammann et al 2019). On the other hand, this work shows that the enhancement of star formation we observe in the LIRGs toward the cluster cores, together with the decrease of the depletion time, implies that the molecular gas reservoirs feeding the star formation exhaust rapidly.…”

“…The presence of enhanced star formation activity observed in a large fraction of the LIRGs within the virial radius suggests that environmental processing mechanisms such as ram-pressure stripping, galaxy harassment, and starvation may have not been sufficiently effective in suppressing the star formation and then quenching the LIRGs. Recent simulations of dwarf galaxies by Hausammann et al (2019) show that, at variance with the hot gas, cold gas may not be efficiently removed by ram pressure.…”

Constraints on the Galactic Inner Halo Assembly History from the Age Gradient of Blue Horizontal-branch Stars

“…While this pressure has the capability to remove cold gas from the satellite and quench star formation, the hot virialized gas in the host galaxy can act to shield the dwarf from both ram pressure stripping and UV-background heating. If we assume the infall of a few (N ∼ 3) progenitors, as suggested from recent observational and simulation studies, then the spread in the BHB age distribution in the IHR of ∼1.0 Gyr suggests either (1) a persistent star formation throughout the merger process, effectively constraining the thermal-to-ram pressure ratio (Hausammann et al 2019) of the mergers that contributed to the formation of the inner halo, or (2) a significant contrast between the ages of the stellar populations contributed to the halo by the Gaia Sausage, Sequoia, and possibly additional dwarf systems yet to be identified.…”

The Tucana dwarf spheroidal galaxy: not such a massive failure after all

“…Piatek & Pryor 1995;Mayer et al 2001aMayer et al ,b, 2006Read et al 2006;Muñoz et al 2008;Klimentowski et al 2009;Kazantzidis et al 2011;Pasetto et al 2011;Battaglia et al 2015;Iorio et al 2019). However, as recently showed by Hausammann et al (2019), the ram-pressure stripping induced by a host halo has its limits in the actual quench and gas depletion of a dSph. Internal effects, like stellar feedback due to episodic star formation and supernova-driven winds, play an important role too (see e.g.…”